A server room of a data center has installed therein a number of server units, generating a large amount of heat. Therefore, it is necessary to efficiently control air-conditioning of the server room of the data center to control the temperature.
In the past, in a server room, an air-conditioning control wherein a temperature of a cool air supply (or blowing out) port of an air-conditioning unit is controlled to be constant, an air-conditioning control wherein a temperature of a warm air return port of the air-conditioning unit is controlled to be constant, or an air-conditioning control wherein a temperature of a wall surface of the server room is controlled to be constant has been performed, for example. Moreover, in some cases, a combination of such air-conditioning controls has been performed.
The server unit is configured to draw outside air through an intake port by means of a fan to thereby cool down an interior of the server room. Therefore, in some cases, an air-conditioning control wherein a temperature of air drawn into the interior of the server unit through the intake port is controlled to be constant has been performed.
As an operating method of a server system having a number of server units, there is known a method wherein some server units are put into a non-operating state during a period where a system load is low. By using such an operating method, it was possible to suppress the power consumption and resultant generated heat of the server system.
FIG. 1 is a diagram illustrating an example of a plurality of server units mounted in a rack with the flow of indrawn air and exhaust air around the rack. When air-conditioning is used to control and maintain a constant temperature of the air drawn through the intake port of each of the server units, the following problems may occur if some server units are put into a non-operating state.
In the server unit in the non-operating state, the rotation of an internal fan thereof is stopped. Therefore, when a non-operating server unit is present among a plurality of operating server units, warm air exhausted from other server units may flow back to an intake port through an exhaust port of the non-operating server unit. As a result, the temperature detected by a temperature sensor mounted in the vicinity of the intake port of the non-operating server unit may exhibit (or indicate) a high value compared with the temperature of cool air supplied from an air-conditioning unit. Therefore, a control device for controlling the air-conditioning within the server room may perform control so that the temperature within the server room becomes lower than a present temperature. Accordingly, it is impossible to perform a suitable temperature control.
Japanese Patent Application Laid-Open No. 2006-208000 discloses a device provided with airflow sensors coupled to a plurality of fans in a server in a data center and a controller for controlling cooling of the data center in accordance with the detected airflow. In addition, Japanese Patent Application Laid-Open No. 2006-208000 describes that a three-dimensional airflow map is generated based on the detected airflow and the fan location. However, according to the invention disclosed in Japanese Patent Application Laid-Open No. 2006-208000, it may be difficult to perform a suitable temperature control when a non-operating server unit is present.
Japanese Patent Application Laid-Open No. 9-298377 discloses a device provided with a temperature sensor for measuring a temperature of air discharged through a ventilation port of a heat exchanger and a flow speed sensor for measuring a flow speed of air discharged through the ventilation port of the heat exchanger. According to the invention disclosed in Japanese Patent Application Laid-Open No. 9-298377, although it is possible to detect a failure of the heat exchanger, it may be difficult to perform a suitable temperature control when a non-operating server unit is present.
Japanese Patent Application Laid-Open No. 2002-032152 discloses a method for automatically interrupting the supply or the cutoff of electric power to an information system based on a comparison between a flow speed measurement of cooling air flowing into the information system and a reference value. According to the invention disclosed in Japanese Patent Application Laid-Open No. 2002-032152, although it is able to detect an abnormality in the flow speed due to a failure or the like of an internal fan and to perform a shutdown process, it may be difficult to perform a suitable temperature control when a non-operating server unit is present.